The idea behind the the meta events were pitched with that same basic concept of a "siege" a page ago. Conceptually, it's the same type of gameplay mechanics as advertised in the shatterer encounters or tacosalad.

Though I always remained skeptical of the open world encounters to actually deliver on those advertisements. That was one of the first multi thread debates I participated in on these forums. With a few regular users pulling their hair out telling me I was wrong.

Speaking of Orr, I really would like to see it evolve. With their living world focus I'm hoping for some permanent changes to the world as a result of it. I actually really like Orr (other than the numerous Risen). And I think it has fascinating lore that should be expanded on. I hope ArenaNet doesn't sleep on it.

It'll be interesting to see how they handle it. It'd be nice if they did something (probably with each expansion) to update some of the areas, such as Orr; while the personal story would no longer be current, they could handle it similarly to how they handled the tutorial content in the GW1 campaigns, as being concurrent with the first campaign, and thus being told the story, rather than living it, while still experiencing it (from a character, rather than player, perspective, of course)

I wonder if Orreans will ever become playable, especially when the Orr zones changes. This came to my mind while talking to an Asura, who found out that the Orreans are just doing what they did in their former life (like farmers etc.) and not out of pure evil.

No, Sylvari can't be resurrected / corrupted in terms of Zhaitan's army afaik. I'm pretty sure it was mentioned in the personal stories.

But yes, I thought about the ancient (human) orreans, forgot all the Asura / Norn / Charr ones for a monent.

It seems they had their rich culture, even the founders of modern Tyria came from Orr. Would it be unlikely to add them as a playable race?
GW1 had only humans, just with different ethnic looks (Cantha/Elona expansions). I often can't tell if someone is a female human or a female norns character.

I tought back when Flame and Frost event begun new xpac gonna come after event is finished. :P

Pretty sure new expac wont be announced until July/August. This patch will be last patch for Flame and Fros and i'm guessing they will do another live story + more additions to the current world (karka island anyone?) before they announce a new expac.